1. Technical Field
The present invention relates to a mask and more particularly, to a face mask for use in delivering an aerosolized drug or the like to a patient.
2. Description of Related Art
Masks are commonly used in a wide range of applications and have widespread use in a number of medical settings. For example, masks are typically used in administering gases to a patient, e.g., an anesthetic agent, and more recently, masks have been increasingly used in drug delivery systems, including nebulizer drug delivery systems and metered dose inhalers using valved holding chambers (MDI/VHC). Nebulization is the application of a drug to a patient by means of an aerosol produced by a flow of gas. The aerosol and the drug are breathed in through the mask and are administered into the respiratory system of the patient as the patient inhales. The MDI/VHC creates its aerosol from the expansion of a volatile liquid into a gas within the VHC.
Nebulization is particularly used in the pediatric field as a means for delivering a drug or the like. In patients, such as young children, who have limited cooperation and attention span, the delivery of an aerosolized drug is carried out primarily with the use of a face mask. The face mask is placed over the nose and mouth of the patient, held in place by a caregiver or by using conventional straps or the like. The face mask is attached to an aerosol drug delivery device. In the case of nebulizers, the face mask is pressurized by the flow from the nebulizer and aerosol fills the mask becoming available for inhalation via the nose or the mouth. When the patient inhales, a negative pressure is applied to the face mask reservoir and the aerosolized drug is inhaled and enters into the respiratory system of the patient.
Metered dose inhalers are also used with face masks to disperse a drug to a patient. These devices dispense a predetermined amount of drug when activated and the patient is required to inhale in order to draw the aerosolized drug into the face mask reservoir and subsequently into the respiratory system of the patient.
Nebulizer drug delivery is different from drug delivery using a metered dose inhaler particularly in the degree of pressurization of the face mask. Metered dose inhalers can pressurize the mask to some degree, especially if aerosol is sprayed directly into the mask and a spacer is not used. A spacer is a device which is placed between the face mask and the source of aerosol (typically a bottle). Often, the spacer has one way valves and therefore is called a “valved holding chamber” (VHC). Face masks are used for both nebulizer drug delivery and for metered dose applications, but there are several associated shortcomings.
Nebulizers readily pressurize the mask and deliver more drug but leaks around the face are enhanced, resulting in increased facial deposition of the drug. Thus, leakage around the mask affects the performance of the particular device and in the case of nebulizers, leakage actually enhances the delivery of the drug; however, it is enhanced at the price of increased facial deposition and potentially local side effects. In order to effectively administer the aerosolized drug into the respiratory system of the patient, the face mask should cover the entire mouth and nasal openings of the patient.
The face mask is generally arranged so that it seats against the cheeks of the patient and extends across an upper portion of the bridge of the patient's nose. Because the bridge of the nose is elevated relative to the rest of the patient's face, e.g., cheeks, the upper portion of the face mask is slightly elevated relative to surrounding portions of the face mask which extend across the cheeks and under the mouth of the patient. This occurs even when the patient attempts to produce a tight seal between the mask and the face. For nebulizers, this produces certain leakage areas where the aerosolized drug can be discharged underneath the face mask and into the atmosphere. Because of the design of face masks and their above-described placement over the face, leakage is universally present in the perinasal areas on either side of the nose. This results in a jet of leaked aerosol being oriented and deposited directly into the eyes of the patient. In other words, aerosol is discharged underneath the face mask in these perinasal areas and flows directly towards the patient's eyes and unfortunately, many of the conventional masks are constructed in such a manner that the leaks that do occur are characterized as being high powered leaks (high kinetic energy) due to the high velocity that the fluid has as it flows underneath the mask and along the face directly into the eyes.
This may lead to several undesired side effects. For example, deposition of the leaked aerosolized drug may be associated with direct trauma to the eyes and associated structures. As leakage occurs, these organs are exposed to the aerosolized drug. There is speculation that the risk of developing cataracts increases as a result of aerosolized drugs being directly deposited in the eyes of the patient. At the very least, leakage of aerosolized drugs causes discomfort as the aerosol, traveling at a great velocity, is discharged underneath the face mask and deposits in the perinasal areas, including the eyes. In addition, leaks of certain aerosols can cause dermatological problems in some patients due to an adverse reaction between facial skin and the aerosol. Other undesirable conditions may result from having the aerosolized drug leaking and being deposited onto the face.
The disadvantages associated with conventional mask constructions are readily apparent by viewing FIGS. 1, 1a and 2. FIG. 1 is a front perspective view of a typical face mask 100 (that is commercially available from Laerdal Medical Corporation of Wappingers Falls, N.Y.). While, the face mask 100 is illustrated as being worn by an adult in FIGS. 1 and 1a, it will be understood that face mask 100 is designed to be worn by small children and finds particular application in pediatric care where the patient is unable or uncooperative in the administration of the drug. The face mask 100 has a body 102 including a peripheral edge 104 which is intended to engage a face of a patient. The body 102 defines a face mask reservoir in which the patient's nasal openings and mouth are in communication. The body 102 is typically made of a flexible material, such as a thermoplastic, e.g., a PVC material. The body 102 has a central opening 106 defined in part by an annular flange-like member 108 which extends outwardly from an outer surface 109 of the body 102. During use, the member 108 is coupled to other components of a drug delivery system (not shown) to permit delivery of the aerosolized drug. The opening 106 serves as a means for delivering the aerosolized drug to the patient. Depending upon the type of drug delivery assembly that is being used, e.g., a metered dose inhaler or a nebulizer system, the opening 106 receives the aerosolized drug as it is transported to the face mask reservoir defined by the body 102. The breathing action of the patient causes the aerosolized drug to be inhaled by the user and introduced into the patient's respiratory system.
As previously mentioned, one of the deficiencies of the face mask 100 is that leakage areas form around the peripheral edge 104. More specifically, the peripheral edge 104 does not form a complete seal with the face of the patient and accordingly, leakage flow paths 107 with high local velocities are formed at certain areas along the periphery of the face mask 100, especially in perinasal areas 105. In fact, maneuvers to reduce leaks along edge 100 may increase the velocity of leaks in perinasal areas 105. The perinasal areas 105 are particularly prone to the formation of leaks and this results in the aerosolized drug being discharged directly into the eyes and the associated structures. As previously mentioned, there are at least two different types of aerosolized drug delivery systems that are commonly used with a face mask, such as face mask 100. One type utilizes a pressurized metered dose inhaler (MDI/VHC) and the other type utilizes a jet nebulizer.
FIGS. 1 and 1a illustrate the face mask 100 as part of an aerosol drug delivery system that utilizes a jet nebulizer 200. The nebulizer 200 is operatively coupled to a compressor (not shown) which generates compressor air through the nebulizer 200. The nebulizer 200 has a body 210 which is coupled to a hose 220 that connects to the compressor at a first section 222 and is constructed so that compressor air flows therethrough. The drug to be delivered is stored in the body 210 using conventional techniques. A second section 224 of the nebulizer 200 communicates with the face mask reservoir so that the aerosolized drug is delivered into the face mask reservoir. The body 210 can include conventional venting and filtering mechanisms.
During aerosol generation, compressor air flows through the body 210 and into the face mask reservoir. This results in pressurization of the face mask 100 and also facilitates leaks at various locations (especially, the perinasal areas) around the face mask 100 with enhanced facial deposition being realized. Once the face mask 100 becomes fully pressurized, excess compressor air (including the aerosolized drug) is vented through an exhaust vent. This results in some of the aerosolized drug being lost into the surrounding environment. The face mask 100 is partially depressurized when the patient inhales but then as soon as the patient stops inhaling and exhales, the face mask 100 is again fully pressurized because of the continuous flow of the compressor air.
When the face mask is placed on a patient, an imperfect seal between the peripheral edge 104 of the face mask 100 and the patient's face typically results due to a number of factors (including face contour of the specific patient). This occurs for small children, children, and adults. The leaks that occur due to the pressurization of the face mask 100 result in the aerosolized drug flowing according to flow paths indicated by arrows 107. These leaks occur around the nose (perinasal areas), the cheeks and at the chin of the patient. It has also been found that the degree of pressure applied to the mask in an attempt to improve the seal between the face mask and the face does not necessarily improve and may in fact worsen the leakage of the aerosolized drug in the perinasal areas when the patient inhales and draws the aerosolized drug into the face mask reservoir. During therapy, local pressure on standard masks may facilitate high local velocities that can lead to eye deposition. For example a caregiver pressing on the mask can seal leaks along the cheeks but promote leaks around the eyes. The leakage of the aerosolized drug in the perinasal areas results in the aerosolized drug being discharged towards the eyes of the patient at high velocities due to the high kinetic energy of the fluid. This is less than ideal as it may cause discomfort at the very least and may also lead to other medical complications due to the drug being discharged into the eyes of the patient.
Eye deposition is thus particularly a problem for those drug delivery systems that exert greater pressure on the face mask and/or maintain the face mask reservoir under pressure. Because pressurization of the face mask 100 plays an important role in a nebulizer drug delivery system and nebulizers have become an increasingly popular means for delivering an aerosolized drug to a patient in such a manner that exhibits a high degree of pressurization in the face mask, the present applicant has studied the amount of eye deposition which occurs when face mask 100 is used in combination with the nebulizer 200 since the face mask pressurization associated with nebulizer use promotes a higher level of leakage around the eye region.
FIG. 2 is a gamma camera image obtained using a simulator face as part of a radiolabel face deposition study carried out using the face mask 100 of FIG. 1 in combination with the nebulizer 200. In these studies, the face mask 100 was attached to a breathing emulator (not shown) which simulated the breathing pattern of a particular type of patient. The breathing emulator includes a three dimensional, contoured bench model face to which the face mask 100 was attached. A filter was placed in the mouth of the bench model face so as to best determine the inhaled mass (actual quantity of aerosol inhaled) as the filter represents the final path of the particles passing into patient.
By using nebulized radiolabeled saline acting as a surrogate drug in the nebulizer 200, the deposition pattern of the particles can easily by determined. FIG. 2 represents deposition following tidal breathing (also referred to as tidal volume) of 50 ml with a minute ventilation of 1.25 liters/min, a pattern typical of a small child. Airflow from the nebulizer 200 is 4.7 liters/minute and therefore the face mask 100 is highly pressurized. Under these conditions, aerosolized drug leaks from the mask at various points on the face, as evidenced by the concentrated areas appearing in the image. As seen in FIG. 2, there is a high level of deposition in the area of the eyes of the patient and there is also a high level of deposition in the chin and jaw areas of the patient. It will be appreciated that other aerosol drug delivery systems which cause the face mask to become pressurized will likely generate similar data showing eye deposition of the aerosolized drug.
While face masks having been developed with venting mechanisms to cope with the pressurization requirements of a nebulizer or the like, these face masks still suffer from the disadvantage that they have constructions that not only permit aerosolized drug to be discharged in the perinasal areas but more importantly, the aerosolized drug is discharged at high velocities toward the eyes due to the imperfect interface between the face mask and the face. In effect, this imperfect interface “funnels” the aerosolized drug so that the aerosolized drug exits the face mask at a high velocity toward the eyes.
What is needed in the art and has heretofore not been available is a face mask which reduces the inertia of the aerosolized drug in the perinasal areas thus reducing deposition in the region of the eyes by inertial impaction, while maintaining flow of the aerosol into the face mask so that the aerosolized drug is effectively delivered to the respiratory system of the patient. The exemplary face masks disclosed herein satisfy these and other needs.